This investigation is designed to determine the effects of general anesthesia and anesthetic techniques on brain mmtabolism, particularly the effects of carrier-mediated transport of glucose between blood and brain. Studies are carried out in the dog during N2O-O2 anesthesia, as well as during anesthesia with halothane and enflurance. Control studies are carried out during N2O-O2 anesthesia and pulmonary ventilation is controlled to maintain end-tidal PCO2 constant at 35 torr. Cannulae are inserted into the vertebral artery and confluence of the sinuses for drug injection and rapid blood sampling, respectively. The uni-directional transport of isotopically labelled glucose and fructose is measured with an indicator dilution technque, using Na22 as the intravascular marker. Cerebral blood flow is measured by external counting of 133 Xenon. Measurements are made at three levels of blood glucose concentration, ranging from 25 to 350 mg percent.